0
votes
2answers
263 views

How secure would this code be against cryptanalysis?

Simple version: Create software that takes a database of the dictionary, alphabet, and phrases. Randomly generate a database of random strings of letters/numbers/symbols of varying length. Randomly ...
0
votes
2answers
262 views

DES generating the same ciphertext for different plaintexts and identical key

Is it possible to get the same output for DES while the inputs are different while using the same key? The key should not have to be a weak key. If yes could you give me a hint how to show how to do ...
0
votes
5answers
2k views

Why can't you decrypt an encrypted message with just the public key? [duplicate]

How does asymmetric crypto work? For example, if you use PGP in emails, you generate a private key that is known only to you and a public key, which is available to everyone. Is there a simple way ...
0
votes
2answers
248 views

Why are these techniques not feasible to crack RSA?

For $d = e^{-1} \mod \phi(n)$ $$d\cdot e \operatorname{mod} \phi(n)=1$$ $$d = (e^{-1} \operatorname{mod} \phi(n))$$ With having $e$ and $n$, we can calculate the value of $d$ , the private key for ...
0
votes
3answers
222 views

Is there a way to break this encryption?

I was wondering about making up a simple system to encrypt a file: ...
0
votes
3answers
617 views

Security of very simple XOR with random? [duplicate]

I am currently trying to implement a very fast and simple encryption algorithm in Lua for the purpose of using it with ComputerCraft. The main problem is that bitwise operations in Lua (5.2 at least) ...
0
votes
2answers
1k views

RSA PCKS1 v2.1 RSAES-OAEP algorithm

Using RSA public key (n,e) the encryption of a message is c= (m^e) mod n and the corresponding message is decrypted as ...
0
votes
3answers
1k views

Is AES really used for Top Secret stuff?

I've read almost everywhere that AES-256 can be used for Top Secret material (in the US). Is it really used or is it some kind of decoy to hide the more advanced algorithm they might use ?
0
votes
3answers
547 views

What block cipher is used for CBC-MAC?

What block cipher is used for CBC-MAC? DES, AES, 3DES? Or it doesn't matter?
0
votes
1answer
188 views

Trying to understand the use of ECC in TLS certificates

I was looking the certificate of this website: https://www.cloudflare.com that has an ECC based certification. I'm just curious to know if is possible to understand which elliptic curve is used and ...
0
votes
4answers
237 views

Why don’t all AES encryption tools produce the same key from the same password?

Alice and Bob meet regularly. They have agreed face-to-face a 128 bit password which they want use to encrypt/decrypt emails written between them. They decide to use 256-bit AES. Alice wrote her ...
0
votes
3answers
73 views

Is the hash function defined in this exercise collision-resistant?

I have this problem: "Let ${\rm Enc}_k(m)$ a safe block encryption system. We define a hash function $H(m)$ as follows: $m$ will be concatenated with $0$ until $|m|$ is a multiple of ...
0
votes
1answer
58 views

Is it safe to encrypt data by simply randomizing chunks based on a permutation?

Say I want to encrypt the following text: "Today is March the 22nd, 2015". And say want to encrypt 8-byte blocks of data using the following permutation [6,3,0,1,5,7,2,4] to swap characters at those ...
0
votes
3answers
233 views

When is a cipher considered broken?

We've all read how some people claim AES is broken because there was supposedly a way to get the plain text from a cipher text faster than brute-force. But is this the definition? Is a cipher broken ...
0
votes
1answer
101 views

Is there any definition for “generic attack” in context of cryptography or more specific “hash functions”?

I'm searching a definition of "generic attack" in context of cryptography or more specific in context of "hash functions". I searched some books and the web but I did not found any definition for it ...
0
votes
2answers
326 views

Why is ElGamalEngine in bouncy castle restricting input data to be less than the length of the group parameter p?

I am currently using the ElGamalEngine of bouncy castle to implement exponential ElGamal for the purpose of making ElGamal additively homomorphic. To do this i raise the message to be encrypted to the ...
0
votes
1answer
135 views

Why is DDH not hard over $\mathbb{Z}^*_p$?

Why is Diffie-Hellman key exchange not hard over $\mathbb{Z}^{*}_p$?
0
votes
2answers
129 views

Asymmetric encryption that is secure for (almost) any foreseeable future

Recently, I've been reading a couple of papers about building cryptosystems that are secure for up to 30 years. But for some applications, this seems a bit low to me. So I am wondering if considering ...
0
votes
2answers
120 views

Removing “security by obscurity” from port knocking

Every article about port knocking, for instance https://wiki.archlinux.org/index.php/Port_Knocking , declares this method as security by obscurity. Is the following enough to remove that title; a ...
0
votes
2answers
128 views

Will SHA1 or Other Hash Functions Ever Contain Quotes [closed]

I feel foolish asking this, but will the hash generated by SHA-1 or other encryption methods ever have the possibility of containing a quote? Or any other characters that may be escaped such as ", ', ...
0
votes
1answer
196 views

Why does the DES crypto algorithm NOT use 2 rounds?

Now, if we were to go round by round, you could give a distinct reason for not using a single round since after just one round, the right half of the text comes directly, as-is, to form the left half ...
0
votes
2answers
184 views

Factors of RSA modulus

In the article A Method for Obtaining Digital Signatures and Public-Key Cryptosystems, the original RSA article, it is mentioned that Miller has shown that n (the modulus) can be factored using any ...
0
votes
1answer
979 views

Random Number Generator based on AES CTR

I've just about done tinkering with an open source DRBG, and I sure would appreciate a bit of advice from this community. Here's the link to the project, hosted at codeproject.com. It is written in ...
0
votes
2answers
464 views

Pi Message Encryption [duplicate]

I created a simple yet efficient message encrypting page that will encrypt messages using Pi. Though not being an expert in this area, I am nowhere near sure how secure this is and how easy it would ...
0
votes
2answers
153 views

Convert SpookyHash to semi-secure 192bit hash [closed]

What do you think of converting SpookyHash into semi-secure 192bit hash function by this way: increase security by using 8 * 8byte = 512bit blocks instead of 8 * 12byte blocks, but remaining 8 * ...
0
votes
3answers
737 views

Generating a number using SHA512 that users can later verify (once I publish secret seed)

I've wrote following C# method that basically takes 3 seeds and gives you number in 0-100 range. I then use that number for variety of purposes but for this question the most important one is the ...
0
votes
2answers
232 views

Encryption of a number with RSA bigger than $n$

I'm having trouble understanding why encrypting a number $m$, which is larger than $n=p\cdot q$. I've looked into the following threads: Why RSA can't handle numbers above 76? Why does plain RSA ...
0
votes
2answers
131 views

Why use two affine transformations in Multivariate Cryptography?

I'm reading Multivariate Cryptography and would like to know why we use two affine transformations to scramble the central map? Why not use only one?
0
votes
1answer
401 views

Is this encryption scheme perfectly secure?

Let $m = 6$, and let $\mathbb{Z}_m$ denote the set $\{0,…,m-1\}$. Let $X \mod m$ denote the remainder obtained when dividing $X$ by $m$. (a) Consider the symmetric encryption scheme in ...
0
votes
2answers
526 views

One Time Pad Question

I have a ciphertext encoded with One Time Pad. I do not know the key. How can I find the possible keys which when decoded, will result in a meaningful plain text?
0
votes
2answers
111 views

A substitution based on a matrix vector product

I choose at random an invertible square matrix A of size 128 in GF(2). I want to use this matrix as a substitution box. Is this a non linear transformation ? I've seen that substitution boxes are ...
0
votes
1answer
1k views

True 128bit secured password length?

assume we say 128bit keys are secure so a 16 character long password is safe, but if i even use lower case and upper case letters with numbers and special characters on my keyboard its about 80 ...
0
votes
2answers
34 views

OTP same message encrypted twice (with different keys)

Lets say we have a message $m$ that we encrypt with two keys $k_1, k_2$ such that $k_1 \ne k_2$. This will produce two ciphertexts $c_1, c_2$ such that $c_1 = m \oplus k_1, c_2 = m \oplus k_2$. The ...
0
votes
2answers
93 views

What are the advantages of using OFB (Output Feedback Mode)? [closed]

I have a problem with OFB mode, because I have heard that it is stronger than CFB.
0
votes
1answer
55 views
0
votes
2answers
106 views

Can AES be considered as Perfectly Secure?

I am studying about the AES encryption standard, and as I know from the theory there is no known weaknesses today about this block-cipher. I would like to find out or at least to understand what ...
0
votes
3answers
84 views

Is the Salsa20/ChaCha20 keystream generation one-way?

Is it possible to recompute the Salsa20 or ChaCha20 key in a realistic time if the keystream and the nonce are given to an attacker? Or is the keystream generation one-way, like a cryptographic has ...
0
votes
1answer
94 views

Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
0
votes
1answer
115 views

Steganography Decryption From Completely Black Image

I am trying to decrypt a completely black gif that I know has been encrypted by some sort of steganography. I've tried subtracting the bytes of the images with each other, and so far I have gotten a ...
0
votes
1answer
306 views

Why is AES unbreakable?

Why is it said that AES is unbreakable? Brute force attacks would take years to crack it, so is it possible to crack it if the computational speed of machines increase in the following decade?
0
votes
3answers
235 views

Random Galois fields

Note: I have now answered this by my own research and can generate random fields up to G(2^9) in reasonable time. I would need to find more speedups for larger fields. At this time G(2^8) takes a few ...
0
votes
2answers
207 views

suitable programming language for cryptography algorithms [closed]

I know as programming languages C and java , and I know that java is slow so for this reason it is not suitable for cryptography applications espacially low level programming (manipulating bits) , so ...
0
votes
1answer
160 views

Addition / Multiplication modulo 13

I am currently studying Diffie-Helman protocol. In my lecture notes I have a generator g=2 and I'm in group $Z_{13}^*$ . There I calculate a remainder cycle from 1 to 12 with $r =g^i \mod 13 \forall ...
0
votes
2answers
91 views

Bouncy jdk 1.51 Serpent KAT tests vs Nessie vectors

Having a little trouble getting Nessie vectors working with the Bouncy Castle SerpentEngine. Do the Nessie vectors require a mode or some pre-processing? Nessie Serpent 128, set 1, vector 0 reads: ...
0
votes
2answers
235 views

Are all block ciphers FPE (format preserving encryption)?

A FPE preserves the format. There is a correspondence between the format of the ciphertext and the plaintext. Given that a message in some binary enconded format can easily be divded in some ...
0
votes
2answers
224 views

Strategy to crack a presumed substitution cipher

The ciphertext given is: ejitp spawa qleji taiul rtwll rflrl laoat wsqqj atgac kthls iraoa twlpl qjatw jufrh lhuts qataq itats aittk stqfj cae I've done ...
0
votes
2answers
217 views

Why are Fortuna entropy pools reset after a reseed?

I've implemented LibTomCrypt's version of fortuna and am wondering about the pool resetting after a reseed. In fortuna.c in libtomcrypt we have the following (which is that part that adds the entropy ...
0
votes
2answers
91 views

Times of nested algorithms in proofs of security

Proofs of security may be constructed such that an adversary $A$ is used to construct an adversary $A'$. The reduction/algorithm which uses $A$ has to perform a number of computations in order to ...
0
votes
2answers
422 views

Should an AES byte key generated with OpenSSL be converted to hex?

I am generating a key & iv with Ruby's OpenSSL wrapper for an AES CBC 256 setup: ...
0
votes
1answer
368 views

Understanding multiplication in the AES specification

I am reading through the AES specification and am not able to wrap my head around the multiplication definition (section 4.2). Sorry to refer to a spec but AES is the holy grail in crypto so I hope ...

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